"The sadistic violence and brutality ... is not the work of a few rogue officers," the lawsuit alleges. "It is a systemic problem."

The lawsuit also says isolation cells are "unfit for human habitation" because they are "filthy, often streaked with feces and reeking of urine."

A U.S. Department of Justice case led to a 2010 consent decree in which Cook County pledged to provide safe living conditions for inmates and allow independent monitors to conduct reports of the jail twice a year.

"However, little has changed," the lawsuit says.

The suit, which includes accounts from around 100 inmates, was filed by the MacArthur Justice Center and the Uptown People's Law Center in Chicago. It names Cook County Board President Toni Preckwinkle and Dart, among others, as defendants.

Speaking at the jail later Thursday, Dart said he would fight the lawsuit.

"This thing is so outrageous on so many levels ... I don't know where to start," he said.

Dart has frequently raised the problem of overcrowding and a lack of mental health services at the facility. He told reporters Thursday that federal monitors have had "unfettered access" to the jail and to inmates for more than four years.

In a written statement, a spokeswoman for Preckwinkle echoed that. Kristen Mack said the twice-a-year Department of Justice reports "do not appear to support these allegations." But she added, "We take this complaint seriously and will examine it."

The suit asks for a court order halting the alleged abuses and seeks unspecified compensatory damages for at least some plaintiffs.